As an information display device substitutable for liquid crystal information display devices (LCD), with the use of technology such as an electrophoresis method, an electro-chromic method, a thermal method, dichroic-particles-rotary method are proposed.
As for these information display devices, it is conceivable as inexpensive visual display device of the next generation from a merit having wide field of vision close to normal printed matter, having smaller consumption, or having a memory function, as compared with LCD, and spreading out to a display for portable device and an electronic paper is expected. Recently, electrophoresis method is proposed that microencapsulate dispersion liquid made up with dispersion particles and coloration solution and dispose the liquid between faced substrates, and also it is expected.
However, in the electrophoresis method, there is a problem that a response rate is slow by the reason of viscosity resistance because the particles migrate among the electrophoresis solution. Further, there is a problem of lacking imaging repetition stability, because particles with high specific gravity of titanium oxide is scattered within solution of low specific gravity, it is easy to subside, difficult to maintain a stability of dispersion state. Even in the case of microencapsulating, cell size is diminished to a microcapsule level in order to make it hard to appear, however, an essential problem was not overcome at all.
Besides the electrophoresis method using behavior in the solution, recently, a method wherein electro-conductive particles and a charge transport layer are installed in a part of the substrate without using solution is proposed. [The Imaging Society of Japan “Japan Hardcopy '99” (Jul. 21-23, 1999) Transaction Pages 249-252] However, the structure becomes complicated because the charge transport layer and further a charge generation layer are to be arranged. In addition, it is difficult to constantly dissipate charges from the electro-conductive particles, and thus there is a drawback on the lack of stability.
As one method for overcoming the various problems mentioned above, an information display, in which one or more groups of display media are sealed between opposed two substrates, at least one substrate being transparent, and, in which the display media, to which an electrostatic field generated between the substrates is applied, are made to move so as to display information such as an image, is known. In the known information display panel of this kind, a glass substrate is often used for the above two substrates, but the information display panel using the glass substrate cannot be applied to a field, which needs flexibility. Therefore, in order to construct the information display panel applicable for the filed, which needs flexibility, the information display panel constructed by using a film substrate as the above substrate is proposed. As one example, there is the information display panel constructed by using a film substrate made of a low permeable film such as PES, PC and so on.
In the information display panel constructed by using the film substrate made of a low permeable film mentioned above, use is made of polyethersulfone (PES) or polycarbonate (PC) as the low permeable film, and such a low permeable film is thick and has a predetermined elasticity. In this case, if a stress such as flexure and so on is applied, a stress is concentrated at a rib adhesion portion and so on of the partition walls, which construct a cell between two substrates, and thus there is a possibility to apply a mechanical damage to the information display panel. Therefore, the substrate, to which an external force is at least applied, needs to be a construction in which a stress concentration can be reduced.